Many present data processing systems have the capacity of adding to the storage capacity of main memory as the need for more storage capacity becomes necessary or desirable. One way of accomplishing this is by adding in modular fashion discrete memory storage units. A data processing system may, as a result, have a main memory comprising a plurality of memory storage units as opposed to one large memory stack.
An inherent problem associated with large storage capacity is the relative slow access time compared to the cycle time of other portions of the computer such as the central processor.
One method of substantially alleviating this problem is by use of a buffer interface disposed between main memory and the processors and the input-output devices. Such an arrangement greatly reduces apparent access time to main memory. The principle which makes this apparent decrease in access time possible is the high probability that data currently being processed stored in buffer storage has a high probability of reuse. This greatly reduces the instances where data has to be retrieved from main memory with consequent apparent speedup in main memory cycle time.
When main memory comprises a plurality of memory storage units, the present invention automatically selects the particular memory storage unit containing the range of addresses expressed in main memory address. Furthermore, the present invention maintains an inventory of the number of main storage units, and the quantity of storage contained in each MSU, and automatically formulates a contiguous addressing range from the available storage when the configuration is changed.
The present invention may be used independently. i.e., as the only interface betweeen main memory and the processor units and input-output units of a data processing system. However; it finds valuable use in conjunction with a high speed storage buffer or cache buffer. The present invention greatly enhances such a high speed buffer by substantially easing the problem of selecting the proper main storage unit.